Characterization of electric properties of nanomaterials usually involves fabricating field effect transistors （FET） and deriving materials properties from device performances. However, the quality of electrode cont...Characterization of electric properties of nanomaterials usually involves fabricating field effect transistors （FET） and deriving materials properties from device performances. However, the quality of electrode contacts in FET devices heavily influences the device performance, which makes it difficult to obtain the intrinsic electric properties of nanomaterials. Dielectric force microscopy （DFM）, a contactless method developed recently, can detect the low-frequency dielectric responses of nanomaterials without electric contact, which avoids the influence of electric contact and can be used to study the intrinsic conductivity of nanomaterials. Here we study the influences of surface adsorbates on the conductivity of ZnO nanowires （NWs） by using FET and DFM methods. The conductivity of ZnO NW is much larger in N2 atmosphere than that in ambient environment as measured by FET device, which is further proven by DFM measurement that the ZnO NW exhibits larger dielectric response in N2 environment, and the influence of electrode contacts on measurement can be ruled out. Based on these results, it can be concluded that the adsorbates on ZnO NW surface highly influence the conductivity of ZnO NW rather than the electrode contact. This work also verifies the capability of DFM in measuring electric properties of nanomaterials.展开更多
Organic micro/nanocrystals based on small organic molecules have drawn extensive attention due to their potential application in organic field-effect transistors,electrochemical sensors,solar cells,etc.Herein,the rece...Organic micro/nanocrystals based on small organic molecules have drawn extensive attention due to their potential application in organic field-effect transistors,electrochemical sensors,solar cells,etc.Herein,the recent advances for organic micro/nanocrystals from the perspective of molecule aggregation mode,morphology modulation,and optical property modulation are reviewed.The stacking mode and the intermolecular interaction depend on the molecular structure,which eventually determines the morphology of organic micro/nanocrystals.The morphologies of the organic micro/nanocrystals make the aggregates exhibit photon confinement or light-guiding properties as organic miniaturized optoelectronic devices.In this review,we conclude with a summary and put forward our perspective on the current challenges and the future development of morphology and optical tunable direction for the organic micro/nanocrystals.展开更多
Nanocrystalline NiFe2O4 particles with mean size of about 20 nm were directly synthesized by a novel microwave-assisted ball-milling approach, using basic nickel carbonate and iron powders as the raw materials. The re...Nanocrystalline NiFe2O4 particles with mean size of about 20 nm were directly synthesized by a novel microwave-assisted ball-milling approach, using basic nickel carbonate and iron powders as the raw materials. The results showed that an interme- diate product Fe2Ni2（OH）sCO3 · 2H2O was formed by milling NiCO3 · 2Ni（OH）2· 4H2O and Fe powders with microwave assis- tance, then this intermediate product further reacted to form NiFe2O4 nanocrystals. On the other hand, by using NiO and Fe2O3 as the raw materials, NiFe2O4 could not be able to form. NiFe2O4 nanocrystals could be directly synthesized without post-sintering by this process. This makes it a new promising approach for ferrite nanoparticle, which is simple and environ- mentally friendly.展开更多
A series of SrTiO3 polyhedral submicro/nanocrystals with systematic morphology evolution from cubic to edge-truncated cubic and truncated rhombic dodecahedra have been synthesized by using a series of alcohol molecule...A series of SrTiO3 polyhedral submicro/nanocrystals with systematic morphology evolution from cubic to edge-truncated cubic and truncated rhombic dodecahedra have been synthesized by using a series of alcohol molecules with different acidities as surfactants. The concentration and pKa value of the alcohols both play important roles in determining the size and shape of the SrTiO3 polyhedral submicro]nanocrystals. The adsorption energy of alcohol molecules on SrTiO3 [110] facets depends on their pKa values, which are therefore critical for morphology control. Using the same strategy, a series of BaTiO3 polyhedral submicro/nanocrystals with systematic morphology evolution have also been successfully prepared.展开更多
We report on a cross-sectional high resolution transmission electron microscope study of lead sulfide nanocrystal quantum dots （NCQDs） dispersed on electron-transparent silicon nanopillars that enables nearly atomic...We report on a cross-sectional high resolution transmission electron microscope study of lead sulfide nanocrystal quantum dots （NCQDs） dispersed on electron-transparent silicon nanopillars that enables nearly atomically-resolved simultaneous imaging of the entire composite： the quantum dot, the interfacial region, and the silicon substrate. Considerable richness in the nanocrystal shape and orientation with respect to the substrate lattice is observed. The average NCQD-substrate separation is found to be significantly smaller than the length of the ligands on the NCQDs. Complementary photoluminescence measurements show that light emission from PbS NCQDs on silicon is effectively quenched which we attribute to intrinsic mechanisms of energy and charge transfer from PbS NCQDs to Si.展开更多
Lead halide perovskite nanocrystals(NCs)exhibit high photoluminescence quantum yield(PLQY),high defect tolerance,narrow half peak width,and wide luminous gamut,making them the ideal optoelectronic materials in numerou...Lead halide perovskite nanocrystals(NCs)exhibit high photoluminescence quantum yield(PLQY),high defect tolerance,narrow half peak width,and wide luminous gamut,making them the ideal optoelectronic materials in numerous fields.Nonetheless,their production still suffers from the limited productivity at the bench level.In this work,we fabricated CsPbX3(X=Cl,Br,I)NCs within droplet-based micro-reactors,where both the nucleation and growth processes could be precisely controlled inside 130-nL microdroplets.This provides a new paradigm for the large-scale synthesis of perovskite NCs with high PLQY.Compared with other synthetic methods,this method can increase the concentration of reactant precursors by 3±116 times,while lowering the ligand to reactant ratio to 2%±50%of the commonly used hot-injection method.By modulating the reaction temperature and residence time,the structure-function relationship between the morphology of NCs and PL properties was extensively investigated.The microfluidic-based process allows the flexible adjustment in the proportion of PbX2 precursors to achieve the fabrication of perovskite NCs whose luminescence range covers the entire visible spectrum(406±677 nm)within one reaction.Finally,perovskite NCs with different halide ions were encapsulated in polymethyl methacrylate to prepare a colored light-emitting diode strip.展开更多
文摘Characterization of electric properties of nanomaterials usually involves fabricating field effect transistors （FET） and deriving materials properties from device performances. However, the quality of electrode contacts in FET devices heavily influences the device performance, which makes it difficult to obtain the intrinsic electric properties of nanomaterials. Dielectric force microscopy （DFM）, a contactless method developed recently, can detect the low-frequency dielectric responses of nanomaterials without electric contact, which avoids the influence of electric contact and can be used to study the intrinsic conductivity of nanomaterials. Here we study the influences of surface adsorbates on the conductivity of ZnO nanowires （NWs） by using FET and DFM methods. The conductivity of ZnO NW is much larger in N2 atmosphere than that in ambient environment as measured by FET device, which is further proven by DFM measurement that the ZnO NW exhibits larger dielectric response in N2 environment, and the influence of electrode contacts on measurement can be ruled out. Based on these results, it can be concluded that the adsorbates on ZnO NW surface highly influence the conductivity of ZnO NW rather than the electrode contact. This work also verifies the capability of DFM in measuring electric properties of nanomaterials.
基金supported by the National Natural Science Foundation of China(21971185)the Collaborative Innovation Center of Suzhou Nano Science and Technology(CIC-Nano)the"111"Project of The State Administration of Foreign Experts Affairs of China。
文摘Organic micro/nanocrystals based on small organic molecules have drawn extensive attention due to their potential application in organic field-effect transistors,electrochemical sensors,solar cells,etc.Herein,the recent advances for organic micro/nanocrystals from the perspective of molecule aggregation mode,morphology modulation,and optical property modulation are reviewed.The stacking mode and the intermolecular interaction depend on the molecular structure,which eventually determines the morphology of organic micro/nanocrystals.The morphologies of the organic micro/nanocrystals make the aggregates exhibit photon confinement or light-guiding properties as organic miniaturized optoelectronic devices.In this review,we conclude with a summary and put forward our perspective on the current challenges and the future development of morphology and optical tunable direction for the organic micro/nanocrystals.
基金supported by the Program for New Century Excellent Talents in University (Grant No. NCET-10-0360)the Fundamental Research Funds for the Central Universities,Hunan university (Grant No.531107040366)
文摘Nanocrystalline NiFe2O4 particles with mean size of about 20 nm were directly synthesized by a novel microwave-assisted ball-milling approach, using basic nickel carbonate and iron powders as the raw materials. The results showed that an interme- diate product Fe2Ni2（OH）sCO3 · 2H2O was formed by milling NiCO3 · 2Ni（OH）2· 4H2O and Fe powders with microwave assis- tance, then this intermediate product further reacted to form NiFe2O4 nanocrystals. On the other hand, by using NiO and Fe2O3 as the raw materials, NiFe2O4 could not be able to form. NiFe2O4 nanocrystals could be directly synthesized without post-sintering by this process. This makes it a new promising approach for ferrite nanoparticle, which is simple and environ- mentally friendly.
文摘A series of SrTiO3 polyhedral submicro/nanocrystals with systematic morphology evolution from cubic to edge-truncated cubic and truncated rhombic dodecahedra have been synthesized by using a series of alcohol molecules with different acidities as surfactants. The concentration and pKa value of the alcohols both play important roles in determining the size and shape of the SrTiO3 polyhedral submicro]nanocrystals. The adsorption energy of alcohol molecules on SrTiO3 [110] facets depends on their pKa values, which are therefore critical for morphology control. Using the same strategy, a series of BaTiO3 polyhedral submicro/nanocrystals with systematic morphology evolution have also been successfully prepared.
文摘We report on a cross-sectional high resolution transmission electron microscope study of lead sulfide nanocrystal quantum dots （NCQDs） dispersed on electron-transparent silicon nanopillars that enables nearly atomically-resolved simultaneous imaging of the entire composite： the quantum dot, the interfacial region, and the silicon substrate. Considerable richness in the nanocrystal shape and orientation with respect to the substrate lattice is observed. The average NCQD-substrate separation is found to be significantly smaller than the length of the ligands on the NCQDs. Complementary photoluminescence measurements show that light emission from PbS NCQDs on silicon is effectively quenched which we attribute to intrinsic mechanisms of energy and charge transfer from PbS NCQDs to Si.
基金financially supported by the National Natural Science Foundation of China (22025801, 21991101, and 21736006)。
文摘Lead halide perovskite nanocrystals(NCs)exhibit high photoluminescence quantum yield(PLQY),high defect tolerance,narrow half peak width,and wide luminous gamut,making them the ideal optoelectronic materials in numerous fields.Nonetheless,their production still suffers from the limited productivity at the bench level.In this work,we fabricated CsPbX3(X=Cl,Br,I)NCs within droplet-based micro-reactors,where both the nucleation and growth processes could be precisely controlled inside 130-nL microdroplets.This provides a new paradigm for the large-scale synthesis of perovskite NCs with high PLQY.Compared with other synthetic methods,this method can increase the concentration of reactant precursors by 3±116 times,while lowering the ligand to reactant ratio to 2%±50%of the commonly used hot-injection method.By modulating the reaction temperature and residence time,the structure-function relationship between the morphology of NCs and PL properties was extensively investigated.The microfluidic-based process allows the flexible adjustment in the proportion of PbX2 precursors to achieve the fabrication of perovskite NCs whose luminescence range covers the entire visible spectrum(406±677 nm)within one reaction.Finally,perovskite NCs with different halide ions were encapsulated in polymethyl methacrylate to prepare a colored light-emitting diode strip.
